What are you considering for paragon path?

Painful Oath is in Dragon Magazine issue 382. Once a turn (not just per round), your hit against your oathie deals an extra [WisMod] necrotic and radiant. And using the Rules Compendium rule on adding damage types, that tacks on necrotic and radiant to whatever other damage types you're using, too.

Power Attack is actively bad for your average damage output, because it makes you miss considerably more. Avenger can use it better than any other class but that -2 to hit does still hurt them. The only time I'd use it is with the Storvakal paragon path, which eliminates up to 2 points in attack penalties as a level 11 feature.

Improved Defenses feat from Heroes of the Fallen Lands or Heroes of the Forgotten Kingdoms would be handy for your NADs. It's a +2 feat bonus to all three, compared with the +3 to one that you get from Great Fortitude. Also, if you prefer to focus on Fortitude, there's now Superior Fortitude which does everything GF does plus a bit of resistance to ongoing damage. It's in the same two books as Improved Defenses.

If you're using a gouge, consider the Carnage Weapon enchantment for a good boost to average damage. I like putting that on any weapon that rolls two small dice per [W], so there's more chance of it triggering.